Astronomy and Cosmology

You must know this representation of the expansion of the universe. It is published in several places on the web. In fact, this representation is a Space-Time diagram. WMAP is the point where we are today as observers of the Universe. _The Big Bang happened 13,7 billions years ago, in the past. The past is on the left side of the diagram. The present time is where the WMAP sattelite is pictured. The future is on the right side. Time goes from left to right. _Each slice of the diagram represents space at a specific period. 3d space has been reduced to a 2d surface. What part of the diagram are we looking at when focusing with our telescopes? Roughly, it …

Presumably, when the universe formed from Alan Guth's inflaton, its hyperbolic gravitational field began to collapse into a parabolic one (see post of Sept. 19, 2011). That collapse continues to this day. But, the process is almost done. There cannot be an infinite amount of gravitational energy sequestered in the hyperbolic field that would be available to fuel acceleration of the expansion rate via such a transformation. That is, transition to a lower energy parabolic field must provide a distinctly limited supply of extra impetus. Surely, after 13.72 billion years, the spring has almost run down by now. If the expansion rate is called h, and its present value is ca…

First, in a flat, matter-dominated cosmos, the age of the universe is 2/3 H0-1. For H0 ~ 70 km/s/Mpc, that age is cosmologically calculated to be >9 Gyr. Second, our sun has a B-V color index of ~0.6, approximately the MS Turn-Off, of the Globular Cluster 47 Tucanae: And, GCs are nearly as old as our universe, i.e. ~9 Gyr for a flat, matter-dominated cosmology. QUESTIONS: First, if our cosmos turns out to be nearly flat, and mostly matter-dominated; then, would not GCs be ~9 Gyr old; and would not our sun's MS lifetime be about ~9 Gyr as well ? Second, if our sun's MS lifetime is typically predicted to be ~10 Gyr; and, if our sun represents …

Please consider a spheroidal 'Dark Matter' (DM) halo, of total mass M; characteristic scale radius R; and, a power-law DM 'particle' Initial Mass Function (IMF), i.e. [math]N(m) \propto m^{-\alpha}[/math] (cp. galaxy luminosity function, star IMF). We shall require that the DM IMF be 'steep', i.e. [math]\alpha > 2[/math] (see below). Normalizations: W.h.t.: [math]M = \int_{m_0}^{\infty} m N(m) dm[/math] [math] = C \times \int_{m_0}^{\infty} m^{1-\alpha} dm[/math] [math] = C \times \frac{1}{\alpha - 2} \frac{1}{m_0^{\alpha-2}}[/math] [math]\therefore C = (\alpha-2) M m_0^{\alpha-2}[/math] Thus: [math]N = \int_{m_0}^{\infty} N(m) d…

The conversational theory of what constitutes a black hole core has resulted in many non-answers, some even dealing with an "infinitesimal singularity" which I find ridiculous. Why not just take a logical step back and conclude that a black hole, and its core, is simply a very large, dense neutron star! That would also keep current laws of physics intact, without all those hypothetical black hole hyperboles. Or has this neutron star thing been rebuffed already? Thanks.

Okay, there probably is a simple answer, but as we know the Earth orbits around the Sun. So, why does it orbit? I know it is partly because it is in the Sun's gravitational field but what gave it the momentum to start orbiting? When a satellite is launched, it needs some initial momentum to push the satellite around the Earth after it escapes the atmosphere. So is this proof that anything with an orbit has had some initial momentum at some point in time, proving the big bang?

Are there any theorys as to the origins of galactic black holes? Could it have been an explosion of a super duperly humungus and ancient super nova?

I have read a couple of previous posts about this, but have wondered if the supposed graviton, if responsible for gravity, could be actually faster than light. My reasoning for this is that if light can't escape a black hole but gravity can, does that not make gravity faster than light?

So, NASA released this amazing topographical map of the far side of the moon, based on images from the Lunar Reconnaissance Orbiter (LRO): (Source: http://www.nasa.gov/mission_pages/LRO/news/lro-topo.html) But this got me thinking. On Earth we define 0-elevation as sea-level. Anything below is negative, anything above is positive. But there's no sea on the moon, or liquid water -- where's the 0-elevation defined, then? Why is this map showing negative elevation values? It just peaqued my curiosity, wasn't entirely sure. Thanks, ~mooey

Would Earth actually burn up if Jupiter were to emit the same powerful source of light as the Sun? Why or why not?

So there's this asteroid called Sylvia. (It's primarily known for having two moons, Remus and Romulus, but that's beside the point.) Sylvia rotates about once every 18661 seconds, sidereally; and her mean radius is about 286 kilometers. That means that, at her equator, assuming approximate sphericity (obviously a big assumption, but that's also beside the point), she rotates at about 96.3 meters per second. But, assuming an object of negligible mass could revolve around her at a non-eccentric distance of exactly her mean radius (again, implausible, but let's not get hung up on that), that object would have an orbital period of (286000^3/(1.478*10^19)/(6.67428*10^…

(realizing that the Physics does not allow for it) "If Jupiter had the same mass it has now but was undergoing nuclear reactions of such a level that it was shining just as bright as our sun, what would that do to our life here on Earth?” All I am asking you to do is to identify ONE thing that would change BUT you must also tell why it would change. Remember – we orbit the sun because of its excessive mass and the mass of Jupiter in this thought problem is NOT to change.

What do you guys think would happen if this was possible? If Jupiter had the same mass it has now but was undergoing nuclear reactions of such a level that it was shining just as bright as our sun, what would that do to our life here on Earth?”

According to John Archibald Wheeler (Journey into Gravity & Space-time): matter tells space-time how to curve; and, curved space-time tells matter how to move Now, beginning about 7 Gya, galaxies had 'clumped' together; and, evacuated inter-galactic deep-space; so that they stopped accreting new, fresh, primordial gas. Thus, galaxy growth has stalled; galaxies today have 10x less gas than 5 Gya; and, galaxies are forming stars 10-30x less rapidly, than 5 Gya (ABC AU 2011). So, if, beginning about 7 Gya, inter-galactic 'voids' had been largely evacuated; and, if local matter-density determines local space-time curvature; then, c.7 Gya, would not most of…

First of all i dont have much knowledge of string theory. String Theory talks about 11-Dimensions. On the other hand all the things or object to which human can observe are 3D and for more details 1 for time, even this too make sense. But according to string theory all the dimensions more than (3+1) are infinitesimal. OK now consider a any mathematical function, f(x,y,z) which when plotted, you can see it in 3D and if you wanna see it more from that than you can zoom up to the limit of your computer performance, memory than also you'll not be available to see any further dimensions. This is not only the case with computer but in real paper and pencil al…

The way I see it, all the time, wherever we look, we are looking into the past. So if you look through a telescope and something that was 10 light years away, then exactly what your seeing would have happened 10 years ago. So while your looking at your computer right now, you are actually seeing the past but on a extremely small scale. Would this be correct?

Since meeting extraterrestrials is unlikely to happen I wonder if just communicating with them would be worthwhile. What I'm trying to determine is if any useful information could be passed between the two civilisations and since all they know about each other is what they are told how much information would they share? Is the search for extraterrestrial life of any value?

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In a previous discussion "Stellar cores - how hot really?" it was mentioned that during the one second in which a Type II supernova creates half the elements heavier then iron, the temperature reaches about FIVE Billion Kelvin. Then a poster said something about a neutron star (at its' core I suppose) the temperature may reach about ONE Trillion Kelvin. Baric: "Temperature is a measure of the average speed of the particles contained within the sample being measured. At some early point after the Big Bang you are no longer dealing with particles so the notion of temperature doesn't apply, at least in a traditional sense. "Also, neutron stars start out at about…

This article suggests that the cosmilogical constant varies, in a smooth manner, relative to the direction of their survey. http://www.dailygalaxy.com/my_weblog/2011/11/stunning-new-stunning-study-of-300-galaxies-shows-some-regions-of-universe-not-fine-tuned-for-life.html#more I think variences do exist but, because they explain this as a smoot transition, I'd say that the light traveling through fields of relativity that exist in our very own galaxy obscurrs the test results.

Well, I was thinking the otherday about the huge amount of light bending around the galaxie like a googilian googilian tiny little electro magnetic fibers. And how some percenage of each ray transfers through the galactic time dialation where it bends and twists around the inner felds of relativity. Amoung the cloud of thoughts I realized that the light going around the time distortion field probably spins the time dialation field. And that there is probably an atmsmasphere of electro magnetic clouds that build up and disapate similar to cloud formations on earth. Especeally towards the outer edge. And that this model suggests that if the clouds become turbu…

If dark matter is clumping at the center of galaxies that will form super massive black holes. Does dark matter interact with the black hole or its gravity?

Hi, I had a look at the Bell Island boom incident and I think it is very interesting and there are a lot of different theories. Personally, I think it was a solar flare which radiated plasma energy, causing electronic disruption, electrocuting animals, blasting holes in the ground, a huge BOOM, and an unexplained ball of light. I would really like to hear some of your theories and views on my theory ( I know it's extremely vague but I'm don't know very much about solar flares and plasma energy. Here are some links: http://en.wikipedia.org/wiki/Bell_Island http://www.stopdirectedenergyweapons.freeservers.com/ http://en.wikipedia.org/wiki/Bell_Island http://www.rum…

How hot are stellar cores really? The Sun's has a core temperature of about 15 million Kelvin but what if a star is 500 or even 1000 times more massive than the sun? What would its core temperature be then? How do you calculate this? Although it's very obvious to me that no electronic component and nothing solid can survive in these temperatures but I would still like to know.

Are there credible theorys out there that suggest that lightning /or some percentage thereof/ is the result of cosmic rays cruzing through the atmosphere? I've read that a bolt of lightning can produce anti matter in high altitudes. It seems reasonable to me that it should take no more energy than this to create matter, like maybe hydrogen from energy. Of course the hydrogen would probably explode from the heat. I guess the waste byproduct of hydrogen would have to be left behind.